UV-B5 charging base

UPDATE 3/23/2025:   

I added an updated version of this model that makes use of the Keystone 5231 battery contact, available via sites like Digikey and Mouser.  The Keystone contact has a 2.5mm hole that I used for assembly with M2.5 cap head screws.  

Model components associated with this update have the phrase “alt_contacts” in the name.  This change makes assembly easier and removes the need to modify a contact before use.  The "socket" component was also tweaked for better radio fit.  Updated source files are included.

Update 3/24/2025

An alternative “socket” component was added.  It has the element “trim” in the name.  It has a reduced front profile, uses less material & will print faster.  It may also aid in assembly by providing better access to the contacts.  Updated source files were included.

Original Description follows:

This model includes components for construction of a DIY DC charging base for UV-B5 radios.  It consists of three printed parts,  charging socket, socket electrical, and cover.    This charging base makes use of a charging control module that incorporates a TP5100 IC.   I used one of these:  https://www.amazon.com/dp/B09QKW6FBV  

Use of this module required configuration for 2S charging at a 1A rate.  See picture for mods.  You remove one surface mount resistor to change charge rate from 2A to 1A.  You solder across two jumper pads to change charge from 1S (4.2v) to 2S (8.4v).

The spring steel contacts I used for the charging base were these:   https://www.amazon.com/dp/B07N2F5W2D ,  which were then modified to fit my application.   Other contacts might be easier to use, but this was readily available & quickly delivered.

I had to make a 90 degree bend to fit the printed mount. The bend was positioned level with the bottom edge of the bent contact end.    Because the spring steel temper was brittle, I had to remove the temper from the area to be bent to avoid breakage.  This was done with a small butane torch, heating the metal to a dull red and then letting it air cool.  The contact was held with flat jaw pliers positioned between the area to be heated and the bent contact areas to protect that area from losing temper.  See the picture to see the area blued from heating on the contact.

There is a two color LED on the charging module that changes color between idle (blue) and charging (red).  Being inside the bottom housing makes this hard to see.  There are three contact positions on the board for using either one two color LED or two mono color LEDs.  The common (center) position is for the anode, the two outer are for cathode connections.  If using a two color LED you need to use a “common anode” version.  The feed beside the +VIN pad is the “idle” circuit.  The feed closest to the GND pad is the “charging” circuit.

I used 3mm discrete LED's and the holes in the electrical box were sized to fit.

Silicon coated,  20awg stranded copper wire is probably the largest size for attachments to this board, silicon coated, 24awg stranded copper was an easier fit for small through holes.

Some versions of the circuit board are not as well labeled as others.  Here are the major landmarks:

I used a pigtail 2.1mm x 5.5mm barrel connector for the power connection.  This allows me to vary the supply source from a wall wart to a 12v DC source as desired.  If configured for 1S, 5 volts will work.  If configured for 2S, you will need 10 - 15 volts (you need a supply voltage higher than the charging voltage.

I secured the charging module to the bottom of the socket component using a bit of servo tape (removable double sided tape with a consistancy of cured rubber cement).   Assembly of the printed components was done with M3 cap head screws.

This UV-B5 charger base can be used for charging a battery either by itself or mounted on the radio

Fusion 360 source and .STEP files are included